Field of the Invention
The present invention relates generally to me infusion pumps, particularly of the type adapted for implantation directed into the body of a patient and for programmed operation to deliver medication to the patient, and more particularly to a reconditioning process for effectively removing accumulated medication-based deposits and the like from internal flow pump passages to restore pump performance characteristics, without requiring an implanted pump to be surgically removed from a patient.
Medication infusion pumps are generally known in the art for use in delivering a selected medication to a patient in a scheduled or preprogrammed manner. In recent years, infusion pumps have been developed in compact form and adapted for direct implantation into the body of a patient, to deliver a specific medication such as insulin to the patient in discrete doses over an extended time period. An implantable infusion pump of this general type includes an internal medication chamber or reservoir for receiving and storing a supply of the selected medication in liquid form, in combination with a miniature pump mechanism and associated programmable control means for operating the pump mechanism to deliver discrete doses of the medication from the internal storage reservoir and through a catheter to the patient. For one illustrative example of an implantable medication infusion pump of this general type, see U.S. Pat. No. 4,573,994, to Fischell et al.
The internal pump mechanism typically comprises an electromagnetically driven pulsatile pump having a solenoid operated piston mounted for reciprocation within a cylinder to draw medication from the storage reservoir, and to deliver the medication through the catheter to the patient. The pulsatile piston operates in conjunction with an inlet check valve having a spring-loaded valve member movable between open and closed positions with respect to an inlet valve seat. The valve member and the valve seat are normally constructed from biocompatible and relatively inert materials, such as a movable valve disk of a silicone elastomer and a rigid annular valve seat defined at the end of a ferrule formed of a titanium or titanium alloy. For examples of pulsatile pump mechanisms used in implantable infusion pumps, see U.S Pat. No. 4,568,250, to Falk et al.; U.S. Pat. No. 4,569,641, to Falk et al.; U.S. Pat. No. 4,636,150, to Falk et al.; and U.S. Pat. No. 4,714,234, to Falk et al.
Despite the relatively inert characteristics of the traditional valve member and valve seat materials, medication deposits having a particle-like structure are known to accumulate over a period of time, especially in the vicinity of the valve seat. The formation of such medication deposits is believed to be attributable to shear denaturation and/or precipitation of pharmaceutical components in response to relatively high mechanical stresses applied to the medication in the immediate vicinity of the valve seat, as the valve member moves between the open and closed positions. Such deposits are especially likely when relatively complex medications having a relatively large molecular structure are used, such as protein-based pharmaceuticals including insulin and others.
Moreover, protein and other organic constituents present in such pharmaceuticals exhibit a tendency to adhere to the surface of titanium metal components, resulting in an accumulation of proteinaceous deposits within internal pump flow passages. Such medication deposits can obstruct narrow flow passages within the pump, resulting in a deterioration in pump performance. Moreover, accumulated deposits at the inlet check valve can over time result in valve leakage, typically in the form of undesirable backflow of body fluids into the medication reservoir. In the past, when these problems have arisen, it has been necessary to use a surgical procedure to remove and replace the infusion pump.
There exists, therefore, a need for a process or procedure for reconditioning an implanted medication infusion pump by safely cleaning and removing the accumulated medication deposits from internal pump flow passages, without requiring surgical removal of the implanted pump from a patient. It is accordingly the objective of the present invention to fulfill these needs and to provide further related advantages.